.fade {
    opacity: 0;
    transition: opacity .15s linear;

    &.in {
        opacity: 1;
    }
}

.collapse {
    display: none;

    &.in {
        display: block;
    }

    // tr&.in    { display: table-row; }
    // tbody&.in { display: table-row-group; }
}

.collapsing {
    position: relative;
    height: 0;
    overflow: hidden;
    transition-timing-function: ease;
    transition-duration: .35s;
    transition-property: height;
}

@mixin rotate($deg: 180deg) {
    -moz-transform: rotate($deg);
    -webkit-transform: rotate($deg);
    transform: rotate($deg);
}